Fix bug in code snippet.

We should set a good example by deleting local refs. as soon as we are
done with, also in our own examples...

Change-Id: Ib9b25b226d79532c137e1c404625840ffd3cdf6e
Reviewed-by: Yoann Lopes <yoann.lopes@digia.com>
Fix note about jni references in documentation.

QAndroidJniObject does not manage user created references regardless
of them being local or global refs.

Change-Id: I4afa8aba8d53f35d83d36758946d4b0f0cb5734a
Reviewed-by: Yoann Lopes <yoann.lopes@digia.com>